Caries detection using timing differentials between excitation and return pulses

ABSTRACT

A laser device is disclosed that directs light to a tooth and analyzes scattered light reflected from the tooth. The device measures a time delay between excitation and reflections of light. Reflected light is analyzed to determine a presence and extent of dental caries on the tooth.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of co-pending U.S. application Ser.No. 11/203,399, filed Aug. 12, 2005 and entitled CARIES DETECTION USINGTIMING DIFFERENTIALS BETWEEN EXCITATION AND RETURN PULSES (Att. DocketBI9895P), which is commonly assigned and the contents of which areexpressly incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electromagnetic energyprocedural devices and, more particularly, to the use of electromagneticenergy device used in dental applications.

2. Description of Related Art

Early detection of dental caries is one important method for promotingdental health. While traditional methods of dental caries detectionrelied upon visual observation by a dental practitioner, othertechniques have been developed that may be capable of augmenting theability of a dental professional to detect dental caries. At least oneof these methods, described more fully in U.S. Pat. No. 5,306,144,entitled DEVICE FOR DETECTING DENTAL CARIES, the entire contents ofwhich are incorporated herein by reference, involves use of a laser thatdirects monochromatic light onto a tooth. Carious areas of the tooth areknown to respond to the light by issuing fluorescent radiation that ischaracteristic of caries and that differs in intensity and spectraldistribution from radiation returned from a healthy tooth. Reflectedradiation may, therefore, be used to detect dental caries. A need existsin the prior art to improve the sensitivity and information content ofdental caries detection.

SUMMARY OF THE INVENTION

The present invention addresses this need by providing a method ofdetecting dental caries comprising directing excitation pulses of laserenergy toward a surface of a tooth and receiving corresponding returnpulses of fluorescent radiation responsive to the laser energy.According to an implementation of the method, a time delay between theexcitation pulses and the return pulses is determined.

An embodiment of the present invention can include an apparatus fordetecting dental caries comprising a laser device capable of generatingexcitation pulses of laser energy, a delivery system capable ofdirecting the excitation pulses toward a surface of a tooth, and adetector capable of receiving return pulses of fluorescent radiationaccording to the excitation pulses. The apparatus further can include acontroller capable of measuring a time delay between transmission ofexcitation pulses and reception of corresponding return pulses.

While the apparatus and method has or will be described for the sake ofgrammatical fluidity with functional explanations, it is to be expresslyunderstood that the claims, unless expressly formulated under 35 U.S.C.112, are not to be construed as necessarily limited in any way by theconstruction of “means” or “steps” limitations, but are to be accordedthe full scope of the meaning and equivalents of the definition providedby the claims under the judicial doctrine of equivalents, and in thecase where the claims are expressly formulated under 35 U.S.C. 112 areto be accorded full statutory equivalents under 35 U.S.C. 112.

Any feature or combination of features described herein are includedwithin the scope of the present invention provided that the featuresincluded in any such combination are not mutually inconsistent as willbe apparent from the context, this specification, and the knowledge ofone skilled in the art. For purposes of summarizing the presentinvention, certain aspects, advantages and novel features of the presentinvention are described herein. Of course, it is to be understood thatnot necessarily all such aspects, advantages or features will beembodied in any particular embodiment of the present invention.Additional advantages and aspects of the present invention are apparentin the following detailed description and claims that follow.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is a pictorial diagram of a delivery system capable oftransferring electromagnetic energy to a treatment site in accordancewith an example of the present invention;

FIG. 2 is a pictorial diagram illustrating detail of a connectoraccording to an example of the present invention;

FIG. 3 is a perspective diagram of an embodiment of module that mayconnect to a laser base unit and that may accept the connectorillustrated in FIG. 2;

FIG. 4 is a front view of the embodiment of the module illustrated inFIG. 3;

FIG. 5 is a cross-sectional view of the module illustrated in FIG. 4,the cross-section being taken along a line 5-5′ of FIG. 4;

FIG. 6 is another cross-sectional view of the module illustrated in FIG.4, the cross-section being taken along a line 6-6′ of FIG. 4;

FIG. 7 is a pictorial diagram of an embodiment of the conduit shown inFIG. 1;

FIG. 8 is a partial cut-away diagram of a handpiece tip in accordancewith an example of the present invention;

FIG. 8 a is a pictorial diagram of detail of the handpiece tip of FIG. 8illustrating a mixing chamber for spray air and water;

FIG. 9 is a sectional view of a proximal member of FIG. 7 taken alongline 9-9′ of FIG. 7;

FIG. 10 is a cross-sectional view of a handpiece tip taken along line10-10′ of FIG. 8;

FIG. 11 is a cross-sectional diagram of another embodiment of thehandpiece tip taken along the line 10-10′ of FIG. 8;

FIG. 12 is a cross-sectional diagram of another embodiment of theelectromagnetic energy handpiece tip taken along line 12-12′ of FIG. 8;and

FIG. 13 is a flow diagram depicting an implementation of a method ofdetecting dental caries according to an implementation of the presentinvention;

FIG. 14 is a flow diagram illustrating a technique for determining arelative time delay in accordance with an example of the presentinvention; and

FIG. 15 is a block diagram of a portion of an exemplary apparatus thatmay be used to detect dental caries according to an implementation ofthe present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference will now be made in detail to the presently preferredembodiments of the invention, examples of which are illustrated in theaccompanying drawings. Wherever possible, the same or similar referencenumbers are used in the drawings and the description to refer to thesame or like parts. It should be noted that the drawings are insimplified form and are not to precise scale. In reference to thedisclosure herein, for purposes of convenience and clarity only,directional terms, such as, top, bottom, left, right, up, down, over,above, below, beneath, rear, and front, are used with respect to theaccompanying drawings. Such directional terms should not be construed tolimit the scope of the invention in any manner.

Although the disclosure herein refers to certain illustratedembodiments, it is to be understood that these embodiments are presentedby way of example and not by way of limitation. The intent of thefollowing detailed description, although discussing exemplaryembodiments, is to be construed to cover all modifications,alternatives, and equivalents of the embodiments as may fall within thespirit and scope of the invention as defined by the appended claims. Itis to be understood and appreciated that the process steps andstructures described herein do not cover a complete process flow foroperation of laser devices. The present invention may be practiced inconjunction with various techniques that are conventionally used in theart, and only so much of the commonly practiced process steps areincluded herein as are necessary to provide an understanding of thepresent invention. The present invention has applicability in the fieldof laser devices in general. For illustrative purposes, however, thefollowing description pertains to a medical laser device and a method ofoperating the medical laser device to perform surgical functions.

Referring more particularly to the drawings, FIG. 1 is a pictorialdiagram of a delivery system capable of transferring laser energy to atreatment site. The illustrated embodiment comprises an electromagneticenergy handpiece 20 that connects to an electromagnetic energy baseunit, such as a laser base unit 30, using a linking element 25. Thelinking element 25 may comprise a conduit 35, which may include one ormore optical fibers, tubing for air, tubing for water, and the like. Thelinking element 25 further may comprise a connector 40 that joins theconduit 35 to the laser base unit 30. The connector 40 may be anidentification connector as is described more fully in U.S. applicationSer. No. 11/192,334, filed Jul. 27, 2005 and entitled IDENTIFICATIONCONNECTOR FOR A MEDICAL LASER HANDPIECE, the entire contents of whichare incorporated herein by reference. The electromagnetic energyhandpiece 20 may comprise an elongate portion 22 and a handpiece tip 45formed as an extension of the elongate portion 22. The elongate portion22 may have disposed therein a plurality of optical fibers that mayconnect to, or that are the same as the optical fibers included in theconduit 35. A proximal (i.e., relatively nearer to the laser base unit30) portion 21 and a distal (i.e., relatively farther from the laserbase unit 30) portion 50 may be disposed at respective proximal anddistal ends of the electromagnetic energy handpiece 20. The distalportion 50 has protruding therefrom a fiber tip 55, which is describedbelow in more detail with reference to FIG. 8. As illustrated, thelinking element 25 has a first end 26 and a second end 27. The first end26 couples to a receptacle 32 of the laser base unit 30, and the secondend 27 couples to the proximal portion 21 of the electromagnetic energyhandpiece 20. The connector 40 may connect mechanically to the laserbase unit 30 with a threaded connection to the receptacle 32 that formspart of the laser base unit 30.

An embodiment of a connector 40 is illustrated in greater detail in FIG.2. The illustrated embodiment comprises a laser beam delivery guideconnection 60 that may comprise, for example, a treatment optical fiber65 capable of transmitting laser energy to the electromagnetic energyhandpiece 20 (FIG. 1). The illustrated embodiment further comprises aplurality of ancillary connections comprising, in this example, afeedback connection 115, an illumination light connection 100, a sprayair connection 95, and a spray water connection 90, that may connect tothe laser base unit 30 (FIG. 1). The plurality of ancillary connectionsfurther may comprise connections not visible in FIG. 2 such as anexcitation light connection and a cooling air connection.

The embodiment of the connector 40 illustrated in FIG. 2 furthercomprises a threaded portion 70 that may mate with and thereby providefor connection to the receptacle 32 on the laser base unit 30 (FIG. 1).

FIG. 3 is a perspective diagram of an embodiment of a module that mayconnect to, and form a part of, a laser base unit 30 (FIG. 1) and thatfurther may accept connector 40 (FIG. 2). The illustrated embodimentcomprises a plate 75 that may fasten to a laser base unit 30 by meansof, for example, screws inserted into holes 76. The module comprises areceptacle 32 that may be threaded on an inside surface 80 to mate withthreads 70 on the connector 40 (FIG. 2). (Threads are not shown in FIG.3.) The embodiment of the module further comprises a laser energycoupling 61 mated to the laser beam delivery guide connection 60 (FIG.2), the laser energy coupling 61 being capable of providing laser energyto the delivery system. The embodiment further comprises a plurality ofancillary couplings including a spray air coupling 96, a spray watercoupling 91, a cooling air coupling 111, and an excitation lightcoupling 106. The embodiment still further comprises a feedback couplingand an illumination light coupling that are not visible in the diagram.One or more key slots 85 may be included to assure that the connector 40connects to the receptacle 32 in a correct orientation.

FIG. 4 is a front view of the embodiment of the module illustrated inFIG. 3. The view in FIG. 4 illustrates the plate 75 and the holes 76that may be used to secure the plate module to a laser base unit, suchas the laser base unit 30 illustrated in FIG. 1. Further illustrated arethe laser energy coupling 61, feedback coupling 116, the illuminationlight coupling 101, the spray air coupling 96, the spray water coupling91, the cooling air coupling 111, and the excitation light coupling 106.In operation, the spray water coupling 91 mates with and is capable ofsupplying spray water to the spray water connection 90 in the connector40 (FIG. 2). Similarly, the spray air coupling 96 mates with and iscapable of supplying spray air to the spray air connection 95 in theconnector 40. Additionally, the illumination light coupling 101, theexcitation light coupling 106, and the cooling air coupling 111 matewith and are capable of supplying, respectively, illumination light tothe illumination light connection 100, excitation light to theexcitation light connector (not shown), and cooling air to the coolingair connection (not shown) in the connector 40. Further, the feedbackcoupling 116 mates with and is capable of receiving feedback from thefeedback connection 115 in the connector 40. According to anillustrative embodiment, the illumination light coupling 101 and theexcitation light coupling 106 couple light from a light-emitting diode(LED) or a laser light source to, respectively, the illumination lightconnection 100 and the excitation light connection (not shown). Oneembodiment employs two white LEDs as a source for illumination light.Also illustrated in FIG. 4 are key slots 85 that may prevent theconnector 40 from being connected to the receptacle 32 in an incorrectorientation.

FIG. 5 is a cross-sectional view of the module illustrated in FIGS. 3and 4. The cross-section is taken along line 5-5′ of FIG. 4, the line5-5′ showing cross-sections of the laser energy coupling 61, thefeedback coupling 116, and the spray water coupling 91. A water source120 may supply water to the spray water coupling 91.

FIG. 6 is another cross-sectional view of the module illustrated inFIGS. 3 and 4. The cross-section of FIG. 6 is taken along line 6-6′ ofFIG. 4. The diagram depicts cross-sections of a light source (e.g., anLED 140) that may be capable of supplying light to, for example, one orboth of the illumination light coupling 101 (FIG. 4) and the excitationlight coupling 106. A pneumatic shutter 125 may control a position of aradiation filter 130 disposed in the laser base unit 30 so that thefilter is either inserted or removed from a light path originating withthe light source (e.g., the LED 140). For example, one or more pneumaticshutter filters may be provided that enable switching between, forexample, blue and white light that is coupled to the illumination lightcoupling 101 and the excitation light coupling 106 in order to enhanceexcitation and visualization.

FIG. 7 is a pictorial diagram of an embodiment of the conduit 35 shownin FIG. 1. The illustrated embodiment of the conduit 35 comprises aplurality of proximal members, such as, four proximal members comprisingfirst proximal member 36, second proximal member 37, third proximalmember 38, and fourth proximal member 39. First, second, and thirdproximal members 36, 37, and 38 may have hollow interiors configured toaccommodate one or more light transmitters or other tubular or elongatestructures that have cross-sectional areas less than a cross-sectionalarea of a hollow interior of the conduit 35. According to oneembodiment, first proximal member 36 comprises an illumination fiber,second proximal member 37 comprises an excitation fiber, and thirdproximal member 38 comprises a feedback fiber. First, second, and thirdproximal members 36, 37, and 38 may be arranged such that the hollowinterior of each proximal member is in communication with a hollowinterior of elongate body 22 (FIG. 1). This arrangement provides for asubstantially continuous path for the light transmitters to extend fromthe proximal portion 21 to the distal portion 50 of the electromagneticenergy handpiece 20.

In accordance with an aspect of the present invention, the thirdproximal member 38 may be configured to receive feedback (e.g.,reflected or scattered light) from the electromagnetic energy handpiece20 and may transmit the feedback to the laser base unit 30. Waveguidescarried by the third proximal member may be positioned to surround atreatment optical fiber 400 (FIG. 8, infra) at an output or distal end50 of the electromagnetic energy handpiece as is more particularlydescribed below.

The fourth proximal member 39 may comprise a laser energy fiber thatreceives laser energy derived from an erbium, chromium, yttrium,scandium, gallium, garnet (Er, Cr:YSGG) solid state laser disposed inthe laser base unit 30 (FIG. 1). The laser may generate laser energyhaving a wavelength of approximately 2.78 microns at an average power ofabout 6 W, a repetition rate of about 20 Hz, and a pulse width of about150 microseconds. Moreover, the laser energy may further comprise anaiming beam, such as light having a wavelength of about 655 nm and anaverage power of about 1 mW transmitted in a continuous-wave (CW) mode.The fourth proximal member 39 may be coupled to or may comprise thetreatment optical fiber 65 (FIG. 2) that receives laser energy from thelaser energy coupling 61 (FIG. 4). The fourth proximal member 39 furthermay transmit the laser energy received from the laser base unit 30 tothe distal portion 50 of the electromagnetic energy handpiece 20 (FIG.1).

Although the illustrated embodiment is provided with four proximalmembers, a greater or fewer number of proximal members may be providedin additional embodiments according to, for example, the number of lighttransmitters provided by the laser base unit 30. In addition, theillustrated embodiment includes first and second proximal members 36 and37 that have substantially equal diameters and a third proximal member38 that has a diameter less than either of the diameters of the firstand second proximal members 36 and 37. Other configurations of diametersare also contemplated by the present invention. In an exemplaryembodiment, the proximal members connect with the connections in theconnector 40 illustrated in FIG. 2. For example, the first proximalmember 36 may connect with the illumination light connection 100 and thesecond proximal member 36 may connect with the excitation lightconnection (not shown). The third proximal member 38 may connect withthe feedback connection 115, and the fourth proximal member 39 mayconnect with the laser beam delivery guide connection 60 and thetreatment optical fiber 65. Attachment of the proximal members 36-39 tothe connections may be made internal to connector 40 in a manner knownor apparent to those skilled in the art in view of this disclosure andis not illustrated in FIGS. 2 and 7.

FIG. 8 is a partial cut-away diagram of a handpiece tip 45 (cf. FIG. 1)that couples with the laser base unit 30 by means of the linking element25 and the elongate portion 22 of the electromagnetic energy handpiece20. The illustrated embodiment, which is enclosed by an outer surface46, may receive electromagnetic (e.g., laser) energy, illuminationlight, excitation light and the like from the laser base unit 30.Typically, the laser energy and light are received by proximal members36-39 (FIG. 7) as described above and transmitted through waveguides,such as fibers 405 disposed in the elongate portion 22 and the handpiecetip 45 as described below with reference to FIG. 10. For example,illumination light (not shown) may be received by the handpiece tip 45,such as from proximal members 36 and 37 (FIG. 7), carried by fibers 405(FIG. 10, not shown in FIG. 8), and directed toward a first mirror 425disposed within the distal portion 50 of the electromagnetic energyhandpiece 20. The first mirror 425 in the illustrated embodiment directsillumination light toward a plurality of tip waveguides 430 as is moreparticularly described below with reference to FIG. 12. Illuminationlight exiting the tip waveguides 430 may illuminate a target area.

According to one embodiment, concentrated electromagnetic energy, suchas laser energy 401, is received (e.g., through fourth proximal member39 (FIG. 7)) and carried by an internal waveguide such as a treatmentoptical fiber 400. The laser energy 401 may be directed toward a secondmirror 420, which may eclipse at least a part of the first mirror 425relative to a direction of propagation of the illumination light to thefirst mirror 425, the second mirror 420 likewise being disposed in thedistal portion 50 of the electromagnetic energy handpiece 20. The secondmirror 420 may reflect, and thereby direct, the laser energy 401 towardthe fiber tip 55. Relative to the concentrated electromagnetic energy(e.g., laser energy 401), the illumination light may comprise an exampleof additional electromagnetic energy, so described because theillumination light and/or, as described below, excitation light, maycomprise electromagnetic energy exhibiting a relatively low power levelthat is directed to illuminate a portion of a target surface that may,for example, surround a portion of a target surface to which theconcentrated electromagnetic energy is directed. The concentratedelectromagnetic energy (e.g., laser energy 401) may be directed towardthe target surface by the fiber tip 55.

In some embodiments, respective first and second mirrors 425 and 420 maycomprise parabolic, toroidal, and/or flat surfaces. FIG. 8 alsoillustrates a simplified view of a path 445 of cooling air received froma cooling air line (not shown) in the handpiece that may receive coolingair from the cooling air coupling 111 (FIG. 4).

The fiber tip 55 illustrated in FIG. 8 may be encased in a tip ferrule105 having a distal end. The tip ferrule 105, together with the fibertip 55, may form a removable, interchangeable unit as is described morefully in U.S. Provisional No. 60/610,757, filed Sep. 17, 2004 andentitled, OUTPUT ATTACHMENTS CODED FOR USE WITH ELECTROMAGNETIC-ENERGYPROCEDURAL DEVICE, the entire contents of which are included herein byreference to the extent not mutually incompatible.

FIG. 9 is a cross-sectional view of first proximal member 36 taken alongline 9-9′ of FIG. 7 demonstrating that first proximal member 36 (as wellas, optionally, second proximal member 37) may comprise three opticalfibers 405 substantially fused together to define a unitary lightemitting assembly or waveguide. In modified embodiments, the threeoptical fibers 405 may be joined by other means or not joined. Accordingto other embodiments, one or more of the proximal members, such as thesecond proximal member 37, can include different numbers of opticalfibers 405. In an illustrated embodiment, the second proximal member 37can include six optical fibers 405 (FIG. 9) that begin to separate andeventually (e.g., at line 10-10′ in FIG. 8) surround a laser energywaveguide, such as treatment optical fiber 400, as illustrated in across-sectional view of FIG. 10 taken along line 10-10′ of FIG. 8 in thehandpiece tip 45. In another exemplary embodiment, the second proximalmember 37 can include three optical fibers 405 (FIG. 9) and the firstproximal member 36 can include three optical fibers 405 (FIG. 9), allsix of which begin to separate and eventually (e.g., at line 10-10′ inFIG. 8) surround a laser energy waveguide, such as treatment opticalfiber 400 in the handpiece tip 45.

FIG. 11 is a cross-sectional diagram of another embodiment of thehandpiece tip 45, the cross-section being taken along line 10-10′ inFIG. 8. FIG. 11 depicts a laser energy waveguide, such as treatmentoptical fiber 400 surrounded by illumination waveguides, such as fibers405, and feedback waveguides, such as fibers 410, all of which aredisposed within outer surface 46. In a manner similar to that describedabove with reference to FIG. 10, the illumination waveguides, such asfibers 405 may receive light energy from the laser base unit 30 (FIG. 1)by way of illumination light coupling 101 (FIG. 4), illumination lightconnection 100 (FIG. 2), and, for example, proximal members 36 and/or 37(FIG. 7); and fibers 405 may direct the light to the distal portion 50of the electromagnetic energy handpiece 20 (FIG. 8). In modifiedimplementations such as those involving, for example, caries detection,one or more fibers (e.g., fibers 405) may function as illumination,excitation and/or feedback waveguides.

Continuing reference with reference to FIG. 7 and related figures, thethird proximal member 38 may include six relatively smaller fibers 410,as likewise is shown in the cross-sectional view of FIG. 10. The smallerfibers 410 and/or other additional waveguides may be disposed within theouter surface 46. Fibers 410 are illustrated as being separate from eachother, but in additional embodiments two or more of the fibers 410 maybe fused or otherwise joined together. Fibers 405 and 410 can bemanufactured from plastic using conventional techniques, such asextrusion and the like.

According to an aspect of the present invention, the fibers 410 can beconfigured to receive feedback (e.g., reflected or scattered light) fromthe electromagnetic energy handpiece 20. Fibers 410 may be positioned tosurround a treatment optical fiber 400 (FIG. 8, infra) at an output ordistal end 50 of the electromagnetic energy handpiece. In a particularimplementation the fibers 410 can be configured to receive feedback fromthe target surface, while in modified implementations the fibers 410 mayadditionally or alternatively be configured to receive feedback fromcomponents (e.g., optical components) within the electromagnetic energyhandpiece. For example, a modified implementation may comprise feedbackin the form of scattered light 435 (FIG. 8) received from the fiber tip55. As presently embodied, the fibers 410 are positioned to transmit thereceived feedback through the third proximal member 38 and to the laserbase unit 30 (FIG. 1).

Feedback waveguides, such as fibers 410, may receive feedback light fromthe fiber tip 55 (FIG. 8) and may transmit the feedback light to thirdproximal member 38, which couples to or comprises feedback connection115. The feedback light may be received by the feedback coupling 116,which transmits the light to a feedback detector 145 (FIG. 5) disposedin the laser base unit 30 (FIG. 1). In other embodiments, such asdescribed more fully in the above-referenced U.S. application Ser. No.11/192,334 entitled IDENTIFICATION CONNECTOR FOR A MEDICAL LASERHANDPIECE, the laser base unit 30 may additionally supply spray air,spray water, and cooling air to the electromagnetic energy handpiece 20.

FIG. 12 is a cross-sectional diagram of another embodiment of theelectromagnetic energy handpiece tip 45 taken along line 12-12′ of FIG.8. This embodiment illustrates a fiber tip 55 surrounded by a tipferrule or sleeve 105, and, optionally, glue that fills a cavity 130around the fiber tip 55 to hold the fiber tip 55 in place. Tipwaveguides 430 may receive illumination light from first mirror 425(FIG. 8) and direct the illumination light to a target. In someembodiments, fluid outputs 415, which are disposed in the handpiece tip45, may carry, for example, air and water. More particularly,illumination light exiting from the illumination fibers 405 (cf. FIG.11) is reflected by first mirror 425 (FIG. 8) into the tip waveguides430 (FIGS. 8 and 12). While a portion of this illumination light mayalso be reflected by first mirror 425 (FIG. 8) into fiber tip 55, fibertip 55 receives, primarily, a relatively high level of laser energy 401from treatment optical fiber 400 (cf. FIG. 11), which laser energy, aspresently embodied, comprises radiation including both a cutting beamand an aiming beam. In a representative embodiment, illumination lightfrom the illumination fibers 405 that exits the tip waveguides 430 iswhite light of variable intensity (e.g., adjustable by a user) forfacilitating viewing and close examination of individual places of atarget surface, such as a tooth. For example, a cavity in a tooth may beclosely examined and treated with the aid of light from a plurality oftip waveguides 430.

A detailed illustration of an embodiment of a chamber for mixing sprayair and spray water in the handpiece tip 45 is shown in FIG. 8 a. Asillustrated, the mixing chamber comprises an air intake 413 connectedto, for example, tubing (e.g., a spray air line, not shown) thatconnects to and receives air from, the spray air connection 95 in theconnector 40 (FIG. 2). Similarly, a water intake 414 may connect totubing (also not shown) that connects to and receives water from thespray water connection 90 in the connector 40 (FIG. 2). The air intake413 and the water intake 414, which may have circular cross-sectionsabout 250 μm in diameter, join at an angle 412 that may approximate 110°in a typical embodiment. Mixing may occur in a neighborhood where theair intake 413 and water intake 414 join, and a spray (e.g., atomized)mixture 416 of water and air may be ejected through a fluid output 415.The embodiment illustrated in FIG. 12 depicts three fluid outputs 415.These fluid outputs may, for example, correspond to, comprise parts of,or comprise substantially all of, any of fluid outputs described in U.S.application Ser. No. 11/042,824, filed Jan. 24, 2005 and entitledELECTROMAGNETICALLY INDUCED TREATMENT DEVICES AND METHODS, the entirecontents of which are incorporated herein by reference, to the extentcompatible, or, in other embodiments, structures described in thereferenced provisional patent application may be modified to becompatible with the present invention. The fluid outputs 415 may, asillustrated in FIGS. 8 and 12, have circular cross-sections measuringabout 350 μm in diameter.

Scattering of light as described above with reference to FIG. 7 can bedetected and analyzed to monitor various conditions. For example,scattering of an aiming beam can be detected and analyzed to monitor,for example, integrity of optical components that transmit the cuttingand aiming beams. In typical implementations the aiming beam may causelittle to no reflection back into the feedback fibers 410. However, ifany components (such as, for example, second mirror 420 or fiber tip 55)is damaged, scattering of the aiming beam light (which may be red inexemplary embodiments) may occur. Scattered light 435 (FIG. 8) may bedirected by the first mirror 425 into feedback fibers 410 that mayconvey the scattered light to the laser base unit 30 (FIG. 1).

In accordance with an aspect of the present invention, scattering oflight as described above with reference to FIG. 7 can also be used fordetection of various conditions, such as dental caries.

FIG. 13 is a flow diagram that introduces an implementation of a methodof detecting dental caries according to the present invention. Accordingto the illustrated implementation, an excitation pulse of light isdirected toward a tooth surface at step 210. For example, for cariesdetection, illumination light may be received from the laser base unit30 as already described. The illumination light may be transmittedthrough and emitted from the illumination and/or excitation fibers 405(FIGS. 10 and 11) as an excitation pulse in a spectral range (e.g.,range of violet, blue, cyan, green, and yellow light) from about 360 nmto about 580 nm. In a modified embodiment, monochromatic light having awavelength of, for example, about 406 nm (e.g., visible violetwavelengths) can be used instead. Other spectral frequencies or rangesmay be used in other modified embodiments, as well.

A source of the light used for caries detection can comprise, accordingto one embodiment, white light received from at least one white lightemitting diode such as LED 140 (FIG. 6), which is disposed in the laserbase unit 30 and the output of which may or may not be coupled to afilter as described herein. In other embodiments at least one lightsource may comprise a source such as a mercury-vapor lamp, a kryptonlaser, a halogen lamp, or a dye laser as representative examples.According to another implementation, the LED 140 may emit another typeof light (e.g., blue light), which can then be filtered to obtain adesired light output (e.g., white light, or light having a wavelength ina range of about 360 nm to about 420 nm). Accordingly, in typicalimplementations at least one corresponding light filter 135 (FIG. 7) canbe disposed in the path of the radiation generated by the at least onelight source to pass only desired wavelengths of, in an illustratedembodiment, about 360 nm to about 420 nm. Although shown coupled to thefirst proximal member 36 (FIG. 7), light filter 130 or 135 mayadditionally or alternatively be coupled to the second proximal member37 (FIG. 7). In another embodiment, a light filter 130 controlled by apneumatic shutter 125 can be disposed in the laser base unit 30. Thepneumatic shutter 125 can cause the filter 130 to be inserted into orremoved from a light path originating with the light source (e.g., LED140), the light path continuing through, for example, the secondproximal member 37 (FIG. 7). According to yet another embodiment, thepneumatic shutter 125 may switch between white light and any other(filtered) of light.

With reference to the cross-sectional view of FIG. 6, one implementationthat comprises LED 140 for directing light throughpneumatically-controlled shutter filter 130 can supply light to, forexample, excitation light coupling 106 (FIG. 4). The excitation lightcoupling 106 is capable of coupling light into an excitation lightconnection disposed in the connector 40 of FIG. 2, although theexcitation light connection is not visible in the view shown in FIG. 2.According to an exemplary embodiment, the second proximal member 37(FIG. 7) receives light from the excitation light connection andtransmits the light to first mirror 425 (FIG. 8) in the distal portion50 of the electromagnetic energy handpiece 20. Light reflected from thefirst mirror 425 may be directed to, for example, tip waveguides 430 asillustrated in FIGS. 8 and 12. An LED similar to LED 140 (FIG. 6) maydirect light into the illumination light coupling 101 (FIG. 4). Theillumination light coupling 101 may connect with and couple light intothe illumination light connection 100 in the connector 40 illustrated inFIG. 2. Illumination light connection 100 may direct the light to, forexample, first proximal member 36 (FIG. 7), which transmits the light tothe first mirror 425 (FIG. 8), whence the excitation light is directedto tip waveguides 430 (FIGS. 8 and 12). A light source (e.g., LED 140)for the excitation coupling 106 can be of a different type from that ofa light source for the illumination light coupling 101, or the sourcescan be of the same type.

In accordance with one aspect of the present invention, light enteringthe excitation light coupling 106 is pulsed, wherein the pulse durationmay range from about 0.001 to 100 μs. In a representative embodiment,the pulse duration may be about 1 μs. The radiation may comprise asequence of identical pulses, or may comprise sequences of varyingpredetermined pulse shapes, spacings and/or durations according todesired applications in order to facilitate detection and analysis ofcaries and/or other properties of the tooth by way of returned radiationtherefrom according to signal analysis techniques known to those skilledin the art.

According to one embodiment, both illumination and excitation lightsources comprise white-light LEDs but only the radiation entering intothe excitation light coupling 106 is processed to produce light (e.g.,violet light) in a spectral range of about 360 nm to about 420 nm, thelight being pulsed as described above. In another embodiment, theillumination light coupling 101 of FIG. 4 also transmits as anexcitation light coupling, so that two excitation fibers (e.g., firstproximal member 36 and second proximal member 37) direct excitationradiation (e.g., filtered and/or pulsed radiation) from the laser baseunit 30 toward the handpiece 20.

Returning to FIG. 13, carious places of a tooth issue fluorescentradiation (e.g., visible red wavelengths) in response to incidentradiation from an excitation pulse. This fluorescent return pulse isreceived at step 220. More particularly, the fluorescent return pulsemay be received by, for example, the tip waveguides 430 (FIGS. 8 and12). The fluorescent return pulse may permit identification of differenttypes/strains of caries-causing bacteria that return radiation ofdifferent (e.g., varying hues of red) fluorescent wavelengths. Thefluorescent radiation can differ in one or more of intensity, delay andspectral distribution from radiation returned by a healthy tooth, whichradiation may comprise, for example, visible green wavelengths. Thus,carious places of the tooth may appear as bright spots that stand outclearly when displayed against a dark background. Accordingly, acondition of carious disease can be detected with a relatively highlevel of accuracy and reliability, at a relatively early stage.

Radiation returned from a surface of the tooth as a result of reflectionand fluorescence enters the tip waveguides 430 (FIGS. 8 and 12) of thehandpiece 20 (FIG. 1) for processing. Details regarding, for example,generation of excitation light and processing of returned radiation to,for example, remove background noise and facilitate qualitative andquantitative detection of caries, are described in U.S. Pat. No.5,306,144, entitled DEVICE FOR DETECTING DENTAL CARIES, the entirecontents of which are incorporated herein by reference to the extentcompatible with, or modifiable by one skilled in the art to becompatible with, or to the extent not mutually exclusive with, thedisclosure herein.

In an exemplary embodiment, returned radiation received by the feedbackcoupling 116 (FIG. 6) is processed by a first filter (not shown) withinthe laser base unit 30 (FIG. 1), the first filter passing radiation in aspectral range above 620 nm (e.g., above orange light). The radiationpassed by the first filter is thus restricted at a lower end, and socontains mainly fluorescent radiation relatively devoid of interferingbackground radiation having shorter wavelengths.

Wavelengths above an acceptance wavelength of the filter reach the photodetector 145 (FIG. 5) within the laser base unit 30. The photo detector145 is connected to receive filtered radiation from the first filter andto convert the filtered radiation into a first electrical signal forquantitative evaluation. The first electrical signal, which can beindicated in a known manner, is in an illustrated embodimentapproximately proportional to a level of radiation intensity detected bythe photo detector 145 and is thus suitable for use in quantitativeassessment of an extent of a detected caries condition. Consequently,carious places of the tooth can be analyzed.

In one embodiment, the first filter is a narrow band filter that acceptsradiation returned from the tooth at wavelengths of about 636 nm(corresponding to visible red light). A second narrow band filter isalso provided that accepts radiation returned from the tooth atwavelengths of about 550 nm (corresponding to visible green light),which is a peak reflectance wavelength from healthy tooth tissue. Thephoto detector 145 or another photo detector converts the filteredradiation from the second narrow band filter into a second electricalsignal. A quotient formed by dividing the first electrical signal by thesecond electrical can be automatically determined within the laser baseunit 30, and the quotient can be used to provide an indication of apresence of caries. Stated otherwise, a magnitude of a green peak can becompared to a magnitude of a red peak to determine the presence andextent of caries.

As presently embodied, a time delay is detected between a givenexcitation pulse and a corresponding returned pulse at step 230 of theimplementation of the method of the present invention depicted in FIG.13. A relative time delay may also be determined at step 240 of the samefigure. FIG. 14 is a flow diagram illustrating an implementation of amethod of determining relative time delays. According to thisimplementation of the method of the present invention, a running averageof delays between excitation pulses and corresponding returned pulses ismaintained at step 250. A time delay associated with an excitation pulseis received at step 260, and the time delay between a given excitationpulse and the corresponding return pulse is compared with the runningaverage of delays at step 270. In other embodiments, an excitation pulsemay be compared with a corresponding return pulse for differences in atleast one of intensity, delay and spectral distribution. A given timedelay (and/or another difference or other differences) between anexcitation pulse and a corresponding return (e.g., fluorescence) pulsecan provide an indication of a depth of caries, wherein a deeper (e.g.,sub-surface) caries may have a greater delay and/or greater scatteringthan the scattering associated with surface caries or healthy tissue.Different lengths of excitation pulses may be able to facilitate theascertainment of different types of information pertaining to the toothsurface. A more wide-spread caries on a tooth surface may result in, forexample, a return pulse having a longer fluorescence time when comparedwith less widely distributed caries. Also, a presence of different typesof bacteria may be detected to an extent that different types ofbacteria affect one or more characteristics of a return pulsedifferently. For instance, different types of bacteria may havedifferent delay or fluorescence times.

In addition to caries detection, the cutting beam radiation, which,generally, carries a relatively higher power than that of theillumination or excitation light, the cutting beam being emitted fromfiber tip 55 of the handpiece tip 45, can be used for caries therapy. Insuch a case, cutting beam radiation having a wavelength (e.g., violetlight wavelength) in a range from about 360 m to about 420 nm may causecaries pathogens to react sensitively to cutting beam radiation and todie off. Early-stage dental caries treatment with simultaneousobservation of the location of the treatment (e.g., in an iterativefashion, with multiple iterations being performed) may thus beimplemented.

In one embodiment, the tip waveguides 430 (FIGS. 8 and 12) and tipferrule or sleeve 105 are housed (e.g., supported) in a housing 440(FIG. 12) that may comprise, for example, metal. According to oneimplementation, an interior of the housing 440 is solid, with cavitiesdisposed therein for accommodating, for example, the tip ferrule orsleeve 105, and tip waveguides 430, and for defining the fluid outputs415. In other implementations, the housing 440 and/or interior cancomprise a transparent material, such as a transparent plastic,sapphire, or quartz, so that the individual tip waveguides 430 mayoptionally be omitted. Thus, in some embodiments, light can betransmitted through the transparent material of the interior without aneed for disposing or defining tip waveguides 430, so that the interiormay comprise cavities only for the tip ferrule of sleeve 105, and thefluid outputs 415.

Returning to FIG. 11, the illustrated embodiment comprises a laseremitting fiber 400 surrounded by six fibers 405, which may be used forillumination and excitation in implementations involving cariesdetection, and three feedback fibers 410. The fibers 405 may be referredto as illumination/excitation fibers. In other embodiments, greater orfewer numbers, or different dimensions or spacings, of theillumination/excitation fibers 405 (and/or tip waveguides 430) and/orfeedback fibers 410 may be employed. According to one aspect of theinvention, two or more of each, and in a particular implementation threeor more of each, may be used to avoid, for example, shading, which mayresult from using only a single (or two) illumination/excitation fibers405 and/or tip waveguides 430.

In a representative embodiment, the fluid outputs 415 (FIG. 12) arespaced at zero (a first reference), one hundred twenty, and two hundredforty degrees. In another embodiment, the six illumination/excitationfibers 405 and three feedback fibers 410 (FIG. 11) are optically alignedwith and coupled via first mirror 425, for example, on a one-to-onebasis, to nine tip waveguides 430 (FIGS. 8 and 12). For example, if nineelements (e.g., six illumination/excitation fibers 405 and threefeedback fibers 410) are evenly spaced and disposed at zero (a secondreference, which may be the same as or different from the firstreference), forty, eighty, one hundred twenty, one hundred sixty, twohundred, two hundred forty, two hundred eighty, and three hundred twentydegrees, then nine tip waveguides 430 may likewise be evenly spaced anddisposed at zero, forty, eighty, one hundred twenty, one hundred sixty,two hundred, two hundred forty, two hundred eighty, and three hundredtwenty degrees. In another embodiment wherein, for example, the tipwaveguides 430 are arranged in relatively closely-spaced groups of threewith each group being disposed between two fluid outputs, the tipwaveguides 430 may be disposed at, for example, about zero, thirty-five,seventy, one hundred twenty, one hundred fifty-five, one hundred ninety,two hundred forty, two hundred seventy-five, and three hundred tendegrees. In one such embodiment, the tip waveguides 430 may likewise bedisposed at about zero, thirty-five, seventy, one hundred twenty, onehundred fifty-five, one hundred ninety, two hundred forty, two hundredseventy-five, and three hundred ten degrees. Further, in such anembodiment, the fluid outputs may be disposed between the groups of tipwaveguides at about ninety-five, two hundred fifteen, and three hundredthirty-five degrees.

The cross-sectional views of FIGS. 10 and 11 may alternatively (oradditionally), without being changed, correspond to cross-sectionallines 10-10′ taken in FIG. 8 closer to (or next to) first and secondmirrors 425 and 420 to elucidate corresponding structure that outputsradiation distally onto the first mirror 425 and the second mirror 420.The diameters of illumination/excitation fibers 405 and feedback fibers410 may be different as illustrated in FIG. 10 or the diameters may bethe same or substantially the same as shown in FIG. 11. In an exemplaryembodiment, the illumination/excitation fibers 405 and feedback fibers410 in FIG. 11 comprise plastic constructions with diameters of about 1mm, and the tip waveguides 430 in FIGS. 8 and 12 comprise sapphireconstructions with diameters of about 0.9 mm.

FIG. 15 is a block diagram of a portion of an embodiment of an apparatusthat may be used to detect dental caries. The illustrated embodiment,which may be disposed within a laser base unit 30 (FIG. 1) comprises acontroller 500, a timer 505, a light transmitter 510, and a lightreceiver 515. The embodiment further comprises a light splitter 520, afirst light filter 525, a second light filter 530, a first photodetector 535, a second photo detector 540, and a display device 550. Asystem bus 545 provides a communication and control path by means ofwhich the controller 500 is able to control the timer 505 and the lighttransmitter 510. The system bus 545 further provides means for thecontroller 500 to receive electrical signals from first and second photodetectors 535 and 540 and to communicate with the display device 550.

In operation the controller 500 may cause the light transmitter 510 totransmit a pulse of light as described above. The controller 500,further, may communicate with the timer 505 to receive a first timevalue representing a time at which the pulse of light was transmitted.The light may be directed through a connector 40 as illustrated, forexample, in FIG. 1, conveyed through a conduit 35 (FIG. 2), passed to anelectromagnetic energy (e.g., laser) handpiece 20, reflected from afirst mirror 425 (FIG. 8), and directed to tip waveguides 430 (FIG. 8)that direct the light to a target surface, such as a surface of a tooth.Reflected or scattered light 435 (FIG. 8), which may be caused byfluorescence of caries on the tooth, may be directed through tipwaveguides 430 and onto first mirror 425, reflected from the firstmirror 425 and conveyed to the laser base unit 30 (FIG. 1) through theelectromagnetic energy handpiece 20, the conduit 35, and the connector40, and received by a light receiver 515 (FIG. 15).

According to one embodiment, the light receiver 515 directs the light tothe splitter 520 that directs a portion of the light to a first filter525 and that, further, directs another portion of the light to a secondfilter 530. As described above, the first filter 525 may comprise, forexample, a narrow band filter that passes radiation at wavelengths ofabout 636 nm (i.e., substantially visible red light). The second filter530 may comprise a second narrow band filter that passes radiation havewavelengths near 550 nm (i.e., substantially visible green light). Lightfrom the first filter 525 (e.g., red light) may be received by the firstphoto detector 535, which creates a first electrical signal according toan intensity level of the light passed by the first filter 525.Similarly, light from the second filter 530 (e.g., green light) may bereceived by the second photo detector 540, which creates a secondelectrical signal according to an intensity level of the light passed bythe second filter 530. The controller 500 may receive the first andsecond electrical signals and may compute a quotient as alreadydescribed by, for example, dividing a magnitude of the first electricalsignal by a magnitude of the second electrical signal. The controller500 may compare a result of the division with a stored threshold, andmay provide an indication on the display device 550 according to theresult.

The controller 500, further, may communicate with the timer 505 whenfirst and second electrical signals are detected in order to determine atime delay between transmission of the light pulse and reception of acorresponding response. The controller 500 then may provide anindication to the display device 550 according to the time delay.Additionally, the controller 550 may determine a relative time delay asdescribed below with reference to FIG. 14.

According to certain implementations, the output from a power ortreatment fiber can be directed, for example, into fluid (e.g., an airand/or water spray or an atomized distribution of fluid particles from awater connection and/or a spray connection near an output end of thehandpiece) that is emitted from a fluid output of the handpiece above atarget surface (e.g., one or more of tooth, bone, cartilage and softtissue). The fluid output may comprise a plurality of fluid outputs,concentrically arranged around a power fiber, as described in, forexample, U.S. application Ser. No. 11/042,824 and U.S. ProvisionalApplication No. 60/601,415. The power or treatment fiber may be coupledto an electromagnetic energy source comprising one or more of awavelength within a range from about 2.69 to about 2.80 microns and awavelength of about 2.94 microns. In certain implementations the powerfiber may be coupled to one or more of an Er:YAG laser, an Er:YSGGlaser, an Er, Cr:YSGG laser and a CTE:YAG laser, and in particularinstances may be coupled to one of an Er, Cr:YSGG solid state laserhaving a wavelength of about 2.789 microns and an Er:YAG solid statelaser having a wavelength of about 2.940 microns. An apparatus includingcorresponding structure for directing electromagnetic energy into anatomized distribution of fluid particles above a target surface isdisclosed in the below-referenced U.S. Pat. No. 5,574,247, whichdescribes the impartation of laser energy into fluid particles tothereby apply disruptive forces to the target surface.

By way of the disclosure herein, a handpiece has been described thatutilizes electromagnetic energy to diagnose and/or affect a targetsurface. In the case of procedures using optical energy, such as cariesdetection, the handpiece can include one or more power or treatmentfibers for transmitting treatment energy to a target surface fortreating (e.g., ablating) a dental structure, such as a tooth, aplurality of fibers for transmitting light (e.g., blue and/or whitelight) for illumination and/or diagnostics of a target such as a tooth(e.g., and optionally for other procedures such as curing or whitening),and a plurality of fibers for transmitting light from the target surfaceback to a sensor for analysis. In certain embodiments, the fibers thattransmit blue light may also transmit white light. In accordance withone aspect of the invention herein disclosed, a handpiece comprises anillumination tube having a feedback signal end and a double mirrorhandpiece. In any of the embodiments described herein, the light forillumination and/or diagnostics may be transmitted simultaneously with,or intermittently with or separate from, transmission of the treatmentenergy and/or of the fluid from the fluid output or outputs.

In certain embodiments, the methods and apparatuses of the aboveembodiments can be configured and implemented for use (e.g.,simultaneously or intermittently), to the extent compatible and/or notmutually exclusive, with existing technologies including any of theabove-referenced apparatuses and methods. Corresponding or relatedstructure and methods described in the following patents assigned toBioLase Technology, Inc., are incorporated herein by reference in theirentireties, wherein such incorporation includes corresponding or relatedstructure (and modifications thereof) in the following patents which maybe (i) operable with, (ii) modified by one skilled in the art to beoperable with, and/or (iii) implemented/used with or in combination withany part(s) of, the present invention according to this disclosure,that/those of the patents, and the knowledge and judgment of one skilledin the art: U.S. Pat. No. 5,741,247; U.S. Pat. No. 5,785,521; U.S. Pat.No. 5,968,037; U.S. Pat. No. 6,086,367; U.S. Pat. No. 6,231,567; U.S.Pat. No. 6,254,597, U.S. Pat. No. 6,288,499; U.S. Pat. No. 6,350,123;U.S. Pat. No. 6,389,193; U.S. Pat. No. 6,544,256; U.S. Pat. No.6,561,803; U.S. Pat. No. 6,567,582; U.S. Pat. No. 6,610,053; U.S. Pat.No. 6,616,447; U.S. Pat. No. 6,616,451; U.S. Pat. No. 6,669,685; andU.S. Pat. No. 6,744,790.

In view of the foregoing, it will be understood by those skilled in theart that the methods and apparatus of the present invention canfacilitate detection of dental caries using laser devices. While thisinvention has been described with respect to various specific examplesand embodiments, it is to be understood that the invention is notlimited thereto and that it can be variously practiced. Multiplevariations and modification to the disclosed embodiments will occur, tothe extent not mutually exclusive, to those skilled in the art uponconsideration of the foregoing description. Additionally, othercombinations, omissions, substitutions and modifications will beapparent to the skilled artisan in view of the disclosure herein.Accordingly, the present invention should not be limited by thedisclosed embodiments, but is to be defined by reference to the appendedclaims.

1. A method of detecting dental caries, comprising: directing at leastone excitation pulse of electromagnetic energy toward a surface of atooth; receiving at least one corresponding return pulse of radiationresponsive to the electromagnetic energy; and determining at least onetime delay between the at least one excitation pulse and the at leastone corresponding returned pulse.
 2. The method as set forth in claim 1,further comprising determining a relative time delay according to the atleast one time delay.
 3. The method as set forth in claim 2, wherein thedetermining of a relative time delay comprises: maintaining a runningaverage of time delays between excitation pulses and correspondingreturned pulses; receiving a time delay; and comparing the time delaywith the running average.
 4. The method as set forth in claim 1, furthercomprising comparing a returned fluorescent pulse with a correspondingexcitation pulse according to at least one of intensity, time delay, andspectral distribution.
 5. The method as set forth in claim 1, comprisingreceiving an indication of a depth of caries according to the timedelay.
 6. The method as set forth in claim 1, further comprisingdirecting electromagnetic energy toward caries to perform cariestherapy.
 7. An apparatus for detecting dental caries, comprising: anelectromagnetic energy device capable of generating at least oneexcitation pulse of electromagnetic energy; a delivery system capable ofdirecting the at least one excitation pulse toward a surface of a tooth;a detector capable of receiving at least one return pulse of radiationcorresponding to the at least one excitation pulse; and a controllercapable of measuring a time delay between the transmitting of the atleast one excitation pulse and the receiving of the at least one returnpulse.
 8. The apparatus as set forth in claim 7, wherein the detectorcomprises: an electromagnetic radiation receiver for receiving theradiation as fluorescent radiation; a splitter; at least one filter; andat least one photo detector.
 9. The apparatus as set forth in claim 8,wherein the at least one filter comprises a first narrow band filter.10. The apparatus as set forth in claim 9, wherein the first narrow bandfilter passes electromagnetic radiation having wavelengths of about 636nm.
 11. The apparatus as set forth in claim 9, wherein the at least onefilter further comprises a second narrow band filter.
 12. The apparatusas set forth in claim 11, wherein the second narrow band filter passeselectromagnetic radiation having wavelengths of about 550 nm.
 13. Theapparatus as set forth in claim 12, wherein: the at least one photodetector comprises a first photo detector and a second photo detector;the first photo detector is capable of generating a first electricalsignal according to electromagnetic radiation received from the firstnarrow band filter; the second photo detector is capable of generating asecond electrical signal according to electromagnetic radiation receivedfrom the second narrow band filter; the controller is capable ofdetermining a quotient by dividing a magnitude of the first electricalsignal by a magnitude of the second electrical signal; and thecontroller is capable of comparing the quotient with a stored thresholdand of providing an indication on a display device according to theresult of the comparison.
 14. An apparatus capable of detecting dentalcaries, comprising: an electromagnetic energy device capable ofdirecting electromagnetic energy to a surface of a tooth; a detectorcapable of receiving reflected electromagnetic radiation from the toothaccording to the electromagnetic energy; and a controller capable ofmeasuring a time delay according to the electromagnetic energy and thereflected electromagnetic radiation.
 15. The apparatus as set forth inclaim 14, wherein the electromagnetic energy device is further capableof generating a pulse of electromagnetic energy.
 16. The apparatus asset forth in claim 15, wherein: the controller is capable of controllinga timer according to a time of generating the pulse of electromagneticenergy; and the controller is capable of controlling the timer accordingto a time of receiving a pulse of reflected electromagnetic radiationaccording to the generated pulse of electromagnetic energy.
 17. Theapparatus as set forth in claim 16, wherein the controller is capable ofdetermining a running average of time delays, receiving a time delay,and comparing the time delay with the running average.
 18. The apparatusas set forth in claim 17, further comprising: an electromagneticradiation receiver; a splitter; a first narrow band filter; a secondnarrow band filter; a first photo detector; and a second photo detector.19. The apparatus as set forth in claim 18, wherein: the first narrowband filter passes electromagnetic radiation having wavelengths of about636 nm; the second narrow band filter passes electromagnetic radiationhaving wavelengths of about 550 nm; the first photo detector is capableof generating a first electrical signal according to an intensity ofelectromagnetic radiation received from the first narrow band filter;and the second photo detector is capable of generating a secondelectrical signal according to an intensity of electromagnetic radiationreceived from the second narrow band filter.
 20. The apparatus as setforth in claim 19, further comprising a controller configured to receivethe first electrical signal and the second electrical signal, and todetermine a quotient by dividing a magnitude of the second electricalsignal by a magnitude of the first electrical signal.